304 Progress of Foreign Science. 



6. On the Hydroxanthic Acid, and some of its Products and 

 Combinations. By Mr. Will. C. Zeise, Professor of Chemistry 

 in the University of Copenhagen. 



By a series of experiments on the mutual action of carburet of 

 sulphur, potash, and alcohol, Mr. Zeise has obtained results 

 which he regards as very remarkable. 



Potash, or soda, dissolved in alcohol, may be neutralized by 

 carburet of sulphur, although this liquid does not change litmus 

 colour, and does not neutralize the alkalis in their dry state, or 

 when dissolved in water. This phenomenon is owing to the 

 formation of a peculiar acid, by the re-action of the carburet on 

 the alcohol, which is determined by the alkaline body. This 

 new acid contains sulphur, carbon, and hydrogen. It is probable 

 that the first two elements united act in this combination the same 

 part the cyanogen does in hydrocyanic acid ; and that they exist 

 in it, in a different proportion from what they do in the ordinary 

 carburet of sulphur. He has given the name of xanthogcn 

 (derived from ^av^o:; yellow and yiwotu) to this compound radical, 

 because it forms combinations of a yellow colour with some 

 metals; and he has named the new acid, the hydroxanthic, be- 

 cause it is endovved with all the properties of a perfect acid. 



Very pure carburet of sulphur dissolves readily in the alco- 

 holic solution of potash, and there instantly results a greenish- 

 yellow liquid. This is easily observed by employing a solution 

 of potash made in the cold before it has begun to turn brown. 

 If, after having added enough of carburet to neutralize the solu- 

 tion, we expose it to a temperature approaching to 0° C, it will not 

 be long in yielding delicate crystals so abundantly, that we shall 

 soon have a concrete mass. This dried quickly between folds 

 of paper is the hydroxanthate of potash. It is also obtained by 

 evaporation of the neutral liquid, in vacuo, along with sulphuric 

 acid, or even by spontaneous evaporation ; and also by precipi- 

 tation by means of sulphuric ether. 



The process which he has commonly employed for the pre- 

 paration of the hydroxanthate of potash is briefly as follows : — 

 He puts one part of very pure and well calcined potash into a 

 glass bottle, having a ground stopper; he pours on it about 12 

 parts of alcohol, containing about 96 or 98 in volume of pure 

 alcohol ; he next digests the mixture at a temperature of about 

 20° or 24° C, agitating it very often for two or three hours, and 

 then filters the solution. Immediately afterwards he adds very 

 pure carburet of sulphur, till the liquor no longer reddens turmeric 

 paper; in order to be sure of which he puts in a little carburet 

 in excess, that is, till a portion of the liquid poured into water 

 throws up some oily globules. He now pours the liquid into 

 a glass capisule with upright sides. When we employ an ordi- 

 nary capsule, by reason of its great tendency to climb, it rises in 



